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If you took plane blood from a bird and injected it into a frog, then bred the frog with another frog, would you get a different species of animal?
Question Date: 2013-02-17
Answer 1:

No, injecting different blood won’t change the offspring of an animal. I can see where you would get the idea that blood carries information to the next generation. People talk about “blood relatives” and “bloodlines.” But these sayings are just leftovers from old ideas that were disproven long ago, like thinking that loves happens in your heart instead of your brain. Injecting blood into an animal does not change the information that the animal passes to its offspring. To understand why, let’s go back to the start of an animal’s life.

Frogs, birds, and humans all start out as a fertilized egg. This cell has a complete set of DNA for making the individual frog, bird, or whatever. This one cell divides, making two identical cells. They both divide, and so on. But then cells start to specialize. Some cells will go on to be reproductive cells (either eggs or sperm) other cells will go on to be bone cells or skin cells or blood cells. All the cells still have the same complete set of DNA, but some of it is switched off. This all happens as the individual goes from being one cell to a ball of cells, to something that looks like a baby bird, tadpole, or whatever. The DNA in those egg and sperm cells may occasionally be changed by mutation, but that’s just a mistake in copying the DNA.

The idea that what happens in your life changes your offspring is wrong, but many people sort of believe it without realizing it. For example, they may think that if you run a lot, you will have a child who is fast, or if we get our wisdom teeth pulled, our children will be born without them. This is not true. Only changes in the DNA of egg or sperm cells will change the information used to make the next generation.

Why do you think people hundreds of years ago thought blood was so critical? What are the many things that blood does for us?

Thanks for asking,

Answer 2:

The frog's body would probably reject the bird's blood. What this means is that the frog's body (as is typical of most organisms) recognizes what objects are "self" vs. "foreign" through different chemical signals. Furthermore, although there is genetic information in our blood, only the genes carried in our gametes (also known as reproductive or sex cells) can transfer genetic information to offspring.

Answer 3:

If you injected bird blood into a frog, you would just have a frog that had some bird blood. It might get sick from the bird blood, because its body would know that this was strange blood that didn't belong in a frog.

My mother-in-law got a new heart valve, and they used a pig valve that they sewed into her heart! I don't know what they did to the pig valve, so that my mother-in-law didn't get sick from having a pig valve in her heart; but I'm sure they washed it clean and removed all the blood! Maybe my mother-in-law took medicines, too, so that her body wouldn't be able to fight so hard against the pig valve tissue in it.

Keep asking questions!

Best wishes,

Answer 4:

No. First, you would kill the frog you injected the blood into because you would trigger an immune response against the bird blood you injected. Even if the frog survived, the blood would not have gotten into the line of cells that made sperm and/or eggs, which is what determines the DNA of the baby frog, so the baby would still be just a frog.

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